The Chevy’s steering is light and reacts quickly on turn-in. Handling eventually gives way to understeer…

Hmm. Is this a review of the Corvette Z06 Carbon? The new Camaro ZL1? Perhaps a lucky journalist has been permitted to hack a C6.R around Road Atlanta for a few laps? Nope, it’s from Car and Driver‘s recent powder-puff piece on the 2012 Sonic.

You know, the Sonic. The fourteen-thousand-dollar subcompact.

Handling, apparently, “eventually gives way to understeer” in a fourteen-thousand-dollar subcompact. Amazing. I’d figured there would be some kind of hideous snap-oversteer swing-axle murderball hidden inside that bitch. What a joke. Here’s a hint: any time a writer appears to be surprised by understeer in a modern mass-production street car, assume that writer is a moron and close your browser page lest you accidentally catch the stupid through a dirty keyboard or something.

‘Twas not always the case, however. In this article, and a sequel to follow shortly, we will discuss a few things: what understeer really means, why you want it, why it is now the default handling behavior for all “regular” cars, and how making it the default handling behavior is accomplished. Boring stuff, sure — but when you’re done reading it, you will be more qualified to review the Chevrolet Sonic’s handling than the guy who actually got paid to do it.

What is understeer, anyway? The authentic definition is a little bit more complex than we’d like to think, unfortunately. We have to start with the actual mechanics of how a car turns. Imagine that you are driving down the road in a straight line, and that the road on which you are driving is completely level. If you turn the steering wheel, a series of gears, shafts, and joints will cause the angle of the front wheels to change. (Note: you’re not guaranteed to get the same amount of angle on both wheels.)

The wheels will turn and the tires, which are mounted on the wheels, will also turn, although not quite as much. The difference between the amount of angle in the wheels and the amount of angle in the tires is mostly a function of sidewall stiffness and height, plus the height and stiffness of the tread blocks. The more flex you have in the sidewall, the bigger the gap. This is easy to understand, right?

Forcing the tires to approach the road at an angle causes friction, which pushes the front end of your car in the direction you’ve chosen. Naturally, this being all physics-like and complicated, the amount of turn you get never equals the amount of angle you’ve put in the tires. The difference — “slip angle” — is a function of tire traction, road surface, and so on, and it causes heat to build up in the tires. Track time melts tires because of slip angle, not because you’re, like, totally going fast and stuff. High-speed driving, like on the fabled autobahn, does build up heat, but it takes a while to do it. You can run 112-mph rated snow tires to 160mph if you don’t spend more than a moment or two at that speed. I know this, because I’ve done it.

The dictionary definition of “understeer” doesn’t actually exist, but if it did, it would say something like “not getting all the change in direction you’ve requested via the steering wheel.” If you understood the above paragraphs, then you’ve already realized that understeer happens all the time in pretty much every car, every time you turn the steering wheel. Even a Formula One car begins the entry into a turn by “understeering”. Nobody gets all the steer they asked for. That’s physics. Tall tires, complacent sidewalls, and rubber bushings in the suspension just exacerbate the effects.

Most drivers compensate pretty quickly for that built-in understeer after the first few minutes spent driving a car. Unless you’re going from a Lotus to a U-Haul truck, you probably don’t even consciously consider the process. So let’s put “built-in” understeer aside.

Tires, like sophisticated women, don’t respond well to a heavy or inept hand. Each tire has a bell curve of available traction. As you ask for more traction, you get more, until you pass a certain point, and then each additional steering input produces less traction. This graphic explains the concept… I hope.

Note how turning the wheel past a certain point produces less traction. This accounts for the phenomenon known as “the dipshit limit”, which I have observed at many, many press events. It works like this:

Journalist approaches corner “going real fast”.

Journalist cranks the living hell out of the steering wheel.

Understeer occurs.

Journo complains about “heavy understeer at the limit” in print publication.

The cat, bird, or homeless person using the print publication to catch their defecatory material briefly catches sight of such assertion and is quite confused.

Using our graph below, we could see that the typical street tire wants six degrees of steering/slip angle — but our journalist immediately dials-in eight or nine. The result? The car doesn’t handle. A skilled driver would carefully dial-in an amount of steering which corresponds very closely to the maximum amount of traction available from the tire set he or she is using.

There’s another way to generate excessive understeer in a car — use the brakes at the same time. A tire has a fixed amount of traction, and it can use that traction in any direction. Keith Code, the motorcycle writer, called it the “dollar theory”. You can spend a dollar braking, or cornering, or accelerating — but if you combine the inputs, you may not like the results. Many of my fellow journos enter the turn with a foot jammed onto the brake, while they are turning. If you’re using fifty cents’ worth of braking, don’t expect to get more than fifty cents’ worth of turn.

When we combine the two mistakes, it’s easy to see why most cars feel like “understeering pigs” to journalists. They are putting way too much steering into the car, and they are braking while entering the turn. Happens again and again. At any press event where a racetrack is provided, you will see brake lights on all the way through the turns. No wonder they aren’t going very quickly.

How do we mitigate understeer? The easiest way: Get your braking done before the turn. (Trail-braking is something we will discuss another time.) When you turn in, dial your input in slowly and precisely, noting the amount of resistance you’re getting back. If you’re driving an unfamiliar car, turn the wheel until the amount of resistance lessens a bit, then dial back just a touch. You may not be “at the limit” but you won’t be far, either. Try not to hit anything.

In the next article, we will talk about why street cars used to oversteer by default, how that changed, and why that’s a good thing for everybody.

74 Comments on “In Search Of… Understeer...”

Thank you, Jack! I’m glad I am not the only one who has stopped reading reviews upon encountering the standard meaningless characterization of some-or-other car’s steering behavior at the “limit”. It’ll be interesting to see whether this article (and followups) help improve the quality of what gets printed.

Here’s a hint: any time a writer appears to be surprised by understeer in a modern mass-production street car, assume that writer is a moron and close your browser page lest you accidentally catch the stupid through a dirty keyboard or something.

I didn’t see an expression of surprise or shock, just a statement of (what is probably) fact. I don’t see the problem with stating facts.

The average reader probably doesn’t know that cars default to understeer, partly as a matter of physics and partly due to deliberate design. You’re right in that it’s the norm, but I fail to see how that prevents the reviewer from ever mentioning it.

Not at all. Not everyone knows what understeer is, whereas a writer can safely assume that any English speaker will know what a wheel is. These articles are written for a general audience with varying knowledge of cars, not just for tech geeks.

In any case, Mr. Baruth misses the point that there was a comment that preceded the reference to understeer: “The Chevy’s steering is light and reacts quickly on turn-in.”

Unlike understeer at the limit, light steering and a fast steering wheel before the limit are not default outcomes. The useful part of the assessment was the sentence that I just excerpted, as it describes how the car handles prior to the inevitable understeer.

Braking while turning can actually be a good thing but if only done correctly such as a light trail brake with a proper driver behind the wheel. This does not affect understeer as the car can still do those two inputs simultaneously (within moderation). By doing this you can shorten your threshold brake zone and carry more speed into the corner (faster lap times).

I almost never read reviews by today’s auto journalists. It all boils down to most of them know less than I do about how to actually drive a car fast. They should stick to reviewing the exterior and interior look / feel, the cup holders, and mpg. Then have an actual trained Stig on staff to actually review said vehicles performance.

Trail braking works by slowing the front contact patches of the car when the car is not pointed straight ahead. This creates a rotating moment around the front virtual axle, and it is a complex enough issue to deserve a separate discussion.

In addition to Jack’s reply, a small amount of braking will shift weight forward and increase the size of the front tire’s traction circle, while decreasing the size of the rears. Rear tires in a corner with a smaller traction circle will require a larger slip angle to achieve the same sideways force, and thus the rear end will move towards the outside of the corner. Simultaneously, the front tires will have more grip, and therefore require less slip angle to maintain their portion of the sideways force, moving to the inside of the corner. Alternatively, you could use the greater amount of grip in front to keep a similar line (with the tail out a little bit further), but just going faster so the overall forces are higher.

“There’s another way to generate excessive understeer in a car — use the brakes at the same time. A tire has a fixed amount of traction, and it can use that traction in any direction. Keith Code, the motorcycle writer, called it the “dollar theory”. You can spend a dollar braking, or cornering, or accelerating — but if you combine the inputs, you may not like the results. Many of my fellow journos enter the turn with a foot jammed onto the brake, while they are turning. If you’re using fifty cents’ worth of braking, don’t expect to get more than fifty cents’ worth of turn. ”

This statement is maddening for me.

A tires available traction is ruled by nature and described by this equation F=us*Fn. Friction force equals the coefficient of friction times the FORCE NORMAL. Force normal is the force pushing down on the tire. Due to braking causing an increase Fn on the front tires, that tire’s available traction most certainly increases.

That’s not to say it’s faster to drive that way. I’m just pointing this out because I’m an engineer and the statement is false and drives me nuts.

There are *all sorts* of factors which affect a tire’s traction: caster and camber (as noted by other posters), tread squirm, whether you are driving uphill or downhill… and yes, body motion and other weight-transfer factors.

It’s common for racers to briefly tap the brakes to load the front tires, even when it’s not necessary to slow the car.

For the purpose of our discussion, however, the simplified “Dollar theory” works adequately, and it prevents misunderstandings along the lines of “brake hard to get more cornering force”.

From practical experience, as well, I have yet to see sustained braking into a turn create a net positive increase in available lateral traction after the effort of braking is subtracted. Would you agree?

Its slightly more complex than that. The coefficient of friction at a given slip angle in the simplified equation is also a function of the normal force. There is a peak coefficient at some normal force and the coefficient decreases above & below that. It’s called the tire’s load sensitivity. In addition, the ideal normal force will change depending on slip angle, tire construction, material, temperature, pressure, tread pattern etc.

Why should anyone expect a car review to be about how a car drives fast? Shouldn’t the review be about how the car drives the way people actually drive them–you know, normal?

If a reviewer can drive normally and understands how a car behaves normally, then by all means, let him write a review. I couldn’t care less about track times unless I’m going to drive it on the track. Performance is far more than 0-60 or slalom times and max g’s on a skidpad.

I’m not a Journalist, but I too found my limit of grip around a tight bend in a 93′ Eagle Talon awd tsi. I had all of about 85 miles on the odometer and I was going really fast. I really expected for the car to follow my input. Didn’t happen…

Young yuppy neighbour was gifted a TSI for his 16th birthday. He spent the next 6 months body kitting, stereoing, and painting the thing.

When spring arrived, he lacked the licensing necessary to drive said vehicle on the street, so one day, after lovingly washing it, he offered me the keys so I could cruise him out to his favorite peacocking spot.

En route, I took a couple of twistys at a speed high enough to freak out passengers, but easily managed by even my Mazda 323. To my surprise, the talon ignored all of my inputs, and continued toward the ditch. Some wheel sawing and brake thumping rotated the car enough so that I could put the power back on and keep us on the road. Neighbour kid was freaked out enough to ask to be taken home.

Arriving back at home a few minutes later, we were greeted by Angry Neighbour Dad standing on the driveway. Had he got wind of our near crash? No. He wanted an explanation for the greasy tread patterns on his pristine concrete driveway.

“Oh THOSE” says neighbour kid… “That’s just the ArmorAll that I used on the tires.”

The moral? Spray stuff on your sidewalls if you must, but keep it the hell away from the treads. Also: Don’t ever drive anyone else’s car ever.

My friend lets me borrow his fully restored 71 Chevelle convertible from time to time, and I drive that way more conservatively than my 77 Chevelle. Course I helped restore it, and know it in and out, but Its not my car.

I learned the armorall lesson as well, I had AA my spare tire, and didn’t think anything of it, till I had to use it on the rear axle of my Chevelle…. open rear axle and greasy tire coupled with a fairly warmed up V8 make for slow goings till you wear the stuff off, and do heroic burnouts at 1/4 throttle

Meh. Normally I enjoy Jack’s sarcastic wit, but this one is a bit too much. Not everyone is as stupid as Jack likes to make out.

An “understeering pig” is just a car that starts to understeer heavily before it has generated very much cornering force from the front wheels. It’s really not so dumb to review a car and say that it understeers more (i.e., earlier) than one might like, is it? Merely writing that doesn’t make one an incompetent driver / reviewer.

I guess it would depend on the tester. If the tester is not aware that understeer is amplified when you brake while cornering, they might end up giving the vehicle a worse review than it deserves (because their driving might have made the vehicle behave worse than it might have otherwise).

I think Jack’s point is more about questioning the reliability (and knowledge) of the people who test and review vehicles (while also indicating that he can be trusted on these things because he is aware of these issues in his own tests and reviews–which is a good thing).

Although I can see the difference in writing style, and the fact that you’re review goes more into technical detail as to why it’s not a track car, I must say you do reach almost the same conclusion when it comes to it’s track (un)worthiness. But you do seem speak to different audiences.

To your question, yes, you article describes the actual capabilities of the vehicles better.

But on the other hand, you both really seem to reach quite the same conclusion – which is perfectly in line with what I found out when I drove the SRT-8 on Czech B-roads (never venturing to the limit, as caring owner sat beside me).

The thing is just a big, fat boulevard cruiser. On the track, it sucks.

Jonny is more entertaining delivering this information, you go deeper with reasons why it’s so. Neither of you is wrong and there’s room in the world for both writing styls.

P.S.:
Are American auto journos really so crappy behind the wheel? The European ones I’ve seen seemed to have at least a faint idea of they’re doing…

Uh oh. Not only did the author misspell “the” but he appears to be surprised by the understeer in a modern mass-market street car.

“Here’s a hint: any time a writer appears to be surprised by understeer in a modern mass-production street car, assume that writer is a moron and close your browser page lest you accidentally catch the stupid through a dirty keyboard or something.”

I still love ya, Jack, I’m just peevish because of the lack of make-sexy-time in this article.

The word understeer seems to appear in almost every auto review yet until now I have not seen a definition of the word that made sense. The disparagement of mainstream auto journalists is a nice bonus.

Thanks for posting the information, and keep posting the info about how most auto reviews are created. Sometimes we need to know how the sausage gets made.

….great explanation of tire patch dynamics…..shows you were paying attention during the “classroom” segment at the Skip Barber Academy…….Trailbraking 101, class of ’86?. Most students slept thru those early morning sessions, dreaming of the “hands on” afternoon lessons to come, where they would thrash those Crosley (Crossle?, Crosle?)Formula Fords at what they hoped was 10 tenths, get noticed by F1 scouts, and move to Monaco.
I wonder how many of Skip’s thousands of alumnae actually made it into an F1 cockpit? I can think of at least one, besides Mr. Barber himself, of course.

I think even experienced drivers mis-name it sometimes… neutral steer is when the front and rear slip-angles are equal, but even then some people experience it and describe it as ‘understeer’ because they’re focused on the front tires slipping.

I can’t remember which season of Top Gear it was when they did the piece on the *worst* handling cars by sending them through the hammerhead.. a fairly visual depiction.

“In the next article, we will talk about why street cars used to oversteer by default, how that changed, and why that’s a good thing for everybody.”

if everyone on the road was driving cars set up like the original S2000 (lift, partial, and full throttle oversteer), i’d rather just stay home. or drive that Marauder thing they reviewed on Top Gear.

i feel much safer with the ubiquity of marshmallowy FWD cars. i would say that cuts down on accidents, but i was in high school and my Cavalier had a parking brake. so oversteer will always find a way to get you :)

Remember when Schumaucher went from Benetton to Ferrari and Berger and Alesi went the other way? I remember Berger spending the most of the next season spinning off the track because the car was developed for the complete opposite style of driving. In contrast, Schumaucher was not as fast as he could be but the car stayed on the track. It wasn’t until a few more cars until the Ferrari’s were fully optimized to his driving style… but oh my, the super slow motions of him going through the final chicane at Suzaka were a sight to behold.

I had previously thought of understeer as the tendency of a car to track straight until steering inputs were made. Oversteer, I had tought, was the opposite – the tendency of the car to want to go left or right unless it were held to a straight line.

I’m anxious to read the next article about oversteer.

As an aside, my Drivers Ed instructor in HS always taught us to do all our braking before the turn, then accelerate through the turn.

It is. And while the beemers will initially understeer as well, they can use the throttle to make it into neutrality or oversteer (unless they have something REALLY slow, like 520i).

You, on the other hand, can’t continually turn the understeer to oversteer. You can reduce it, you can make the car to oversteer for a PART of the corner by lifting or braking, but unless you do something brutal (handbrake…), you’ll still have understeer.

Not a bad article, but please, if you could use the cornering circle (or oval, depending on tire construction) method of describing the amount of grip each tire has, I’ve found it easier to understand as well as much more accurate.

The amount of grip isn’t simple addition of 50 + 50 = 100% since the vectors are in different directions. Assuming a decently balanced tire that can be approximated with a cornering circle (as opposed to a drag slick that has an oval stretched in the fore-aft direction), if you’re using 50% of the tire’s grip for braking, you still have almost 87% for turning [100% * sin(30) braking, & 100% * cos(30) turning]

Yes, but… as the suspension dives the camber and caster change, which change the shape of your contact patch… Understanding tire traction in a real, dynamic environment requires a lot of math and a lot of computation. Outside of the major series like F1, racers tend to use some very simplistic approximations that work reasonably well in practice.

There’s no way to include all the math in a 900-word article, and an article which does include all the math would basically be the size of War and Peace. Don’t even get me started on how pressure varies between the sidewall and center of the tread! :)

Yea, I realize its basically impossible to lay out all of the complexities of tire dynamics, let alone the effects that suspension motion impose on the tire or transient effects. However, my point was that the friction circle tends to describe tire grip available much more thoroughly, but with only a touch more complexity than simple addition. It can also be more easily used to describe other effects as well, such as the entire circle expanding with weight transfer, or how the shape changes based on type of tire, camber etc.

Speaking as a layperson, who hasn’t been in a physics classroom in 6 years, and who has never really had the desire to “test the limits” or race, I think I understand what you wrote – a little.

Thanks for the read.

If this is at all related, can somebody explain what is meant by fast steering versus slow steering? I’ve been curious since I first heard the terms, even if my main goal in life is to get from point A to B without incident and not racing.

If someone punches you in the face, you fall over. If someone puts their fist against your forehead, then gradually builds up to the same force as the punch, you stand their looking slightly foolish, and perhaps leaning a little.

It gets into static and dynamic friction, elastic and inelastic reactions, and force and impulse. However: Just like water can kill you if you hit it fast enough, but won’t hold you up if you’re drowning, the speed at which a material is forced to react matters. If you try to force the car (tire/suspension/defineyourownboundaries) to react too quickly, it can’t deal with the change, and crashes. If you are smooth, everything adjusts more or less predictably, and you don’t die.

I thought the terms “fast steering” and “slow steering” simply described the steering ratio. Slower steering requires more steering wheel motion/angle to achieve the same front wheel angle as a car with faster steering.

I think you’re all missing the point. It’s a Chevy Sonic, not a Camaro or Corvette. Is this the type of car that anyone would want to drive anywhere close to its handling limits? It’s a small city car. Tell me how it handles city traffic and speed bumps, not how it handles at top speed around a track. Why is every car reviewed as if it should perform like a race car?

Well, if the car in question isn’t a Lotus. One thing that convinced me to buy my Elan was the fact that on the test drive I was wearing work boots and the Elan’s pedals are small. Being in an unfamiliar car, with clunky boots, as I was turning off a main street into a subdivision, I went to brake as I started to commit to the turn. Unfortunately, I couldn’t find the brake pedal quickly enough and couldn’t slow the car. Already committed to the turn I just cranked the wheel farther and, lo and behold, the Elan just went where I steered it.

I assume (possibly incorrectly) that, on average, the buyers of the Sonic will likely drive them harder than the buyers of many ‘sports’ cars. I’d like to know what percentage of BMW or Porsche cars have EVER seen full-throttle to the redline in their existence (not counting valets drivers).

That was a car that developed an appreciable amount of understeer long before any sane limit had been reached. Say, taking a wide corner at just twenty miles an hour…

If the Sonic is more closely related to the old Aveo than the Cruze is to the Forenza, then I can believe understeer is worth mentioning…

—

Lack of talent: I plowed almost halfway across the road in a Forester the other day. My bad. My companion chided me for turning in too late and using too much steering angle. Embarrassing, because I’m usually quicker than he is around track… because I brake early and turn-in smoothly. Or used to. Modern tires have spoilt me, verily.

I know little about race-driving and less about physics, so Jack’s article went pretty well over my head. I always thought understeer was when you take a corner a bit too fast and the car has a tendency to want to spin the back end around on you, while oversteer meant the opposite, a car that tends to want to drive you nose forward into the ditch when pushed a too far. Is that completely wrong?

I get so sick of supposed car guys perpetuating the myth that FWD = understeer, RWD = oversteer. Whenever I tell someone that my Miata is surprisingly neutral tending to oversteer, they say, “Of course, it’s RWD.” Then when I say that my Mk2 Jetta oversteered on brakes or trailing throttle, they just look at me funny. Very few guys realize that handling characteristics cover more than just what happens when you floor the accelerator (not that the Miata will power the tail out much past first gear anyway!).

This article plays into an argument I had with a friend of mine because he thought his bigger, turd-ier, boxier, Volvo 940 handled better than my 850 Wagon (with the optional sports package.) His reasoning? Because my FWD 850 understeered more than his “masculine” (his actual word choice) RWD brick. When I attempted to explain to him that there is more to the whole understeer vs oversteer conundrum, he just simply resorted to calling me stupid and making fun of the fact that I also own a Cadillac SRX (He called it a: “Long, black, turd with a nasty plastic interior and a shitty engine,” that last one is kind of true but it hurt)… I guess you just reminded me I need to find much more becoming friends… Oh agony.

Interesting article, I’m convinced that most people who talk about understeer & oversteer have never experienced either, at for most of those who have it resulted in a crash.

Re the “dipshit limit”, this can bee seen on in-car footage (eg VBH on Fifth Gear) when the car suddenly darts in the direction of the turn as the steering lock is eventually unwound and the tyre climbs back up the steering input curve shown above.